Staple for the suture of the sternum

ABSTRACT

A staple for the suture of the sternum having a central body with right and left threaded ends in which two teeth are screwed able to be introduced into suitable holes made astride a median sternotomy performed on a patient. Rotating the central body draws the teeth together or apart, thus tightening the two halves of the sternum with appropriate tension. The staple is suitable to be tightened by means of an apparatus provided with friction, to give the correct tightening tension. Also described are a method for the suture of the sternum and punch cutter forceps suitable to be used in such operation.

FIELD OF THE INVENTION

The present invention concerns a staple for the suture of the sternum;it is of particular use after operations in which a sternotomy provednecessary, such as in operations of cardiosurgery.

The invention also concerns a method of application of the staple and akit including one or more staples.

The invention also concerns punch cutter forceps to make holes which areable to receive a staple.

PREVIOUS TECHNIQUE

Currently, the sternotomy represents the most commonly practiced systemof access to the thoracic cavity in operations like those ofcardiosurgery. Closure of the sternum, at the end of the operation, iscommonly performed by passing metal wires around the two halves intowhich it has been divided; the wires are wound in front of the sternumwhich are then tightened, thus closing the two parts of the bone. Eachwire can be wound once or twice, in the latter case it is woundcrosswise. Six wires passing once or three times are commonly used forthe complete suture of the sternum. The technique involves variousproblems. Since closure is carried out manually by the surgeon,generally the tension of the wires is unequal, with reduced closingefficacy, with possible dehiscence (the tightest ligature will tend tocut into the bone, thus working loose. In addition, there is often acertain staggering of the two bone halves which are drawn together.

Moreover, the effort required in passing the wires is considerable, andit requires a sharp needle with the risk of lesions to the detriment ofthe surgeon. As for the patient, passing the wire around the sternuminvolves the risk of lesions to the internal thoracic arteries and alsoto the pleurae and the lungs.

Staples have been proposed made of elastic type alloys to be placedastride the sternum to secure the two halves. They are alloys which areable to expand at low temperatures (with the possibility of positioningthe staple astride the sternum) and of regaining their original form atbody temperature. These are very expensive, and besides the fact thatthe tension of the staple cannot be adjusted, thus not solving theproblems of unequal tensions in the various staples, the positionastride the sternum still involves the risk of lesions to the internalthoracic arteries. Another proposed system envisages the opening ofholes, in the sternum, by means of punch cutter forceps, symmetricalwith regard to the sternotomy section. In each pair of symmetrical holesis inserted an elastic staple, kept widened by special forceps. Uponreleasing the forceps the tension of the staple will be determined bythe distance of the holes, which is carefully predetermined. However, acertain irregularity in the positioning of the holes can still produceuneven distribution of the tensions in the staples, and the accuracyrequired during perforation can complicate and lengthen the operation.Moreover, the staples are manipulated by forceps and inserted undertension, thus making the operation more complicated and less easy, andtherefore also potentially injurious.

SUMMARY

The problems discussed above have now been resolved according to thepresent invention by means of a new type of staple for the suture of thesternum, including a central body having at least two opposite threadedparts and at least two teeth each having a threaded end which is able topair up with one of the threaded parts of the central body. According toa preferred aspect of the invention, said central body has an axis ofsymmetry, more preferably is cylindrical and the two opposite threads(that is a right and a left one) are situated at the two ends of thecentral body; the latter will be preferably a hollow cylinder, at leastin part, and the two threads will be internal threads. The two teethwill have a threaded end and a leg forming a certain angle with theformer, preferably an acute angle. The two teeth, obviously threaded oneright and one left, will be approximately L-shaped or, better, shaped inthe form of a “7”. Rotating the central body will draw the two teethtogether or apart, thanks to the opposite threads.

The staple will be preferably made of biocompatible material, morepreferably diamagnetic, so as not to interfere with diagnosis andmonitoring equipment. For example biocompatible steel or titanium alloyscan be used.

LIST OF THE FIGURES

The present invention will now be illustrated by the detaileddescription of a preferred, but not exclusive, embodiment, suppliedpurely by way of example, with the aid of the enclosed figures of which:

FIG. 1 schematically represents a longitudinal section of the centralbody of a staple according to the present invention;

FIG. 2 schematically represents a tooth of a staple according to thepresent invention;

FIG. 3 schematically represents the staple according to the presentassembled invention;

FIGS. 4 a and 4 b schematically represent, in front and side section, anapparatus to give the correct tension to the staple;

FIG. 5 schematically represents, in section, punch cutter forceps tomake holes in a bone, in particular the sternum.

DETAILED DESCRIPTION

With reference to FIGS. 1, 2 and 3 a staple is now described accordingto the present invention. The central body 1 in this case is cylindricaland is hollow. At its ends it has the internal threads 2 and 2′, oneright and one left. The tooth 3 of FIG. 2 has an end 4 that has theexternal thread 6, able to be joined to the thread 2 of the central body1 and a leg 5 that forms a certain angle with the end 4. Preferably theleg 5 will be cylindrical and its axis will form an acute or right anglewith the axis of the threaded end 4. For example, this angle can bebetween 70° and 85°, a preferred value being 80°. The tip 7 of the tooth3 can have advantageously rounded edges, the tip can even behemispherical or of other shape capable of not injuring body tissues; infact it is destined to be introduced into a hole made in the sternum,and is also able to protrude from the hole. The staple also includesanother tooth 3′, a mirror image of the tooth 3. When it is assembled(FIG. 3), rotating the central body around its own axis 8 will screw theteeth 3 and 3′ drawing them together. Rotation in the opposite directionwill unscrew them. The central body can advantageously be knurled on theexternal surface 9 or part of it, or have other means to aid grip(manual or a special apparatus). The staple is intended for the sutureof a sternum (human or also animal) after sternotomy. Sternotomyinvolves the division of the sternum into two with longitudinal section.To perform the suture, the legs 5 and 5′ of the teeth of the staple areinserted into holes made in the sternum astride the sternotomy section.By rotating the central body 1 the legs 5 and 5′ are drawn towards eachother to give correct tension to the staple. When the legs 5 and 5′ forman acute angle with the ends 4 and 4′ of the teeth 3 and 3′, asindicated above, their inclination will help to prevent the withdrawalof the legs from the holes. In addition, the surface of the legs 5 and5′ may advantageously show protuberances, suitable grooves to encouragetheir grip on the bone. According to a possible embodiment the legs canbe threaded, and it is also possible to obtain the teeth from whollythreaded-cylindrical pieces which are appropriately bent. The tension ofa staple can be given by means of an apparatus like that of FIGS. 4 aand 4 b. It has a motor unit 10 powered, for example, by battery orrechargeable batteries, unit that through the means 11 is suitable totransmit the motion (wheels and gears) to rotate the central body 1 of astaple held by special means. The wheel 13 is pressed against the body 1and transmits the motion by friction. The apparatus is equipped withmechanical, electronic or other type of clutch to give the staple apredetermined tension. In this case the means are a pair of supports 12and a tongue 14 removable by operating the lever 19 after screwing hasoccurred. Other embodiments of the staple holding system can beenvisaged, particularly to eliminate the tongue 14, that can keep thestaple pulled aside from the sternum, a staple which must then be pushedfor its total insertion.

A method of operating, for use of the staple according to the presentinvention is as follows.

The sternum is exposed and, for example, with an electrosurgical knife,the line is marked out along which the sternotomy is performed. Pairs ofpoints are marked astride this on which holes are made, generally 5 or 6pairs. They can be marked by using special stencils, or templates havingthe points of the holes marked and references to be placed on the lineof sternotomy, so as to have exact symmetry of the holes as regards thelatter. Otherwise perpendicular lines to that of the sternotomy can bemarked with the electrosurgical knife, on which the holes must beperformed. It is important that the holes of each pair lie with theircentre on one of these lines (so that the tension of the staple actsperpendicularly to the sternotomy and does not exert longitudinalsliding stress on the two hemisterna. The sternotomy is performed, andbefore or, preferably, after the actual operation, the holes are made inthe selected points by using suitable means such as punch cutterforceps, for example like those of FIG. 5, which represent anotheraspect of the invention. A first jaw 20 carries a punching tip 15, forexample a cylinder with sharp edges. Thanks to suitable means, such asthe system of hinges and guides 17 and 18, the tip 15, following astraight line, moves closer to the second jaw 16, between which jaw andthe tip 15 the bone is compressed and cut, in such a way that a smallcylinder thereof is removed. A through hole 22 can be provided on thesecond opposite jaw 16, to receive the tip 15 and permit cutting. Theportion 21 of surface of the second jaw 16 facing the tip 15 can besuitably inclined, with respect to a line perpendicular to the axis 24of the tip 15 so that by inserting the jaw 16, behind the hemisternum tobe pierced and putting the jaw in contact with it, the jaw gives thecorrect inclination to the tip, in order that the hole is inclined in amanner corresponding to the leg of the staple which it is going toreceive. This portion 21 can form an acute angle with the axis 24 of thetip, which is equal to that formed by the leg of a staple tooth with thethreaded end of the tooth (when said angle is acute). In order tocorrectly position the hole (avoiding that it is too far from thesternotomy) a protuberance 23 can be envisaged on the second jaw 16,facing the first jaw 20 at a suitable distance from the end 25 of saidjaw.

After the operation is ended, the hemisterna are brought together bymeans of special approximators, the legs of the teeth of a staple areintroduced into a pair of holes and it is tightened to the desiredtension as seen above. Unlike that with elastic or expandable typestaples, in which the distance between the holes must be precise, sincethe tension placed on the staple is determined by deformation, thestaple according to the invention allows greater freedom thanks to theapplicable tensioning system, which allows punctual consideration of thebone characteristics and other operational requirements.

Since the sternum has a spongy inner layer it is expedient that the legsof the teeth of the staple grip on both the more resistant outer layers.For this purpose staples with legs of such a length will be chosen so asto completely cross the sternum, and, if necessary, protrude by a fewmm. For example, with the inclinations of the leg given above withrespect to the threaded end of the tooth, leg lengths can be comprisedbetween 10 and 20 mm, for they may be for example 15 mm. The teeth canhave diameters of between 1 and 5 mm, for example 2 mm, the central bodybeing dimentioned accordingly. It can have a total length of between 10and 40 mm, for example 20 mm, the distance between the holes to whichthe staple is adapted varying within a wide range, thank to itsadjustability due to the double thread. Dimensions outside the specifiedranges, for particular requirements, are also possible.

In the case of FIGS. 1, 2 and 3 item he noted that the cavity 20 hassuch a diameter to receive part of the threaded ends 4 and 4′ of theteeth. In this way, by appropriately choosing the lengths, the threads 2and 2′ will be completely screwed, whatever is the operative opening ofthe staple.

The invention also concerns a surgical kit including one or more staplesaccording to the present invention and an apparatus equipped with clutchsuitable to rotate the cylindrical body of a staple whose teeth are heldin holes made in a bone, up to a preset tension.

The kit may advantageously include one or more punch cutter forceps ableto make sternal holes of a diameter suited to the staples included inthe kit.

1. Staple for the suture of a sternum, including a central body (1)having at least two threaded parts (2, 2′) with opposite threads and atleast two teeth (3, 3′), each having a threaded end (4, 4′) able toengage one of the threaded parts of the central body.
 2. Staple as inclaim 1 wherein said central body is a hollow cylinder and the twoopposite threads are internal threads situated at the two ends of thecentral body.
 3. Staple as in claim 1 wherein each tooth has one leg (5,5′), having an axis forming a right or acute angle with the threaded end(4, 4′).
 4. Staple as in claim 3 wherein said angle is between 70° and85°.
 5. Staple as in claim 3 wherein the edges of the tip (7) of eachleg are rounded.
 6. Staple as in claim 1 made of biocompatible anddiamagnetic material.
 7. Staple as in claim 1 wherein the externalsurface (9) of the central body is knurled.
 8. Staple according to claim3 wherein the legs of the teeth have a length of between 10 and 20 mm.9. Punch cutter forceps able to pierce a sternum, including a first jaw(20) having a punching tip (15) having an axis (24), a second jaw (16),means (17, 18) able to move the tip, according to a rectilineartrajectory, closer to the second jaw, a portion (21) of surface of thesecond jaw forming an acute angle with the axis of the punching tip. 10.Forceps as in claim 9 wherein said angle is between 70° and 85°. 11.Forceps as in claim 9 or 10 wherein on the second jaw (16) there is aprotuberance (23) facing the first jaw.
 12. Surgical kit including: oneor more staples for the suture of a sternum, said staples including acentral body (1) having at least two threaded parts (2, 2′) withopposite threads and at least two teeth (3, 3′), each having a threadedend (4, 4′) able to engage one of the threaded parts of the centralbody; and an apparatus equipped with clutch able to rotate thecylindrical body of a staple whose teeth are held in holes made in abone, up to a preset tension of the staple.
 13. Surgical kit as in claim12 including one or more punch cutter forceps able to make holes, in asternum, of diameter suitable for one or more staples included in thekit.
 14. Surgical kit as in claim 13 including one or more punch cutterforceps, said forceps-including a first jaw (20) having a punching tip(15) having an axis (24), a second jaw (16), means (17, 18) able to movethe tip, according to a rectilinear trajectory, closer to the secondjaw, a portion (21) of surface of the second jaw forming an acute anglewith the axis of the punching tip.